CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

Simulating aircraft- my l-d values

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   May 6, 2013, 13:50
Default Simulating aircraft- my l-d values
  #1
C_K
New Member
 
Myron
Join Date: May 2013
Posts: 4
Rep Power: 4
C_K is on a distinguished road
Would simulating an accurately created airplane give you the lift and drag values it should achieve in real life?

For example making an airbus a320 which has a weight of say 62000kg-608220N

Should the lift value i get in fluent be around that value in newtons or does Ansys fluent only give the correct cl and cd value that i should expect?

My sim has given me 150000N for half the aircraft- 300000N for full aircraft which is half the value needed to lift the aircraft.

Thanks
C_K is offline   Reply With Quote

Old   May 6, 2013, 21:03
Default
  #2
Senior Member
 
Join Date: Aug 2011
Posts: 315
Rep Power: 12
blackmask will become famous soon enough
Are you sure that you have the right AoA (angle of attack) ? Lift or cl is much easier to predict so that the result of your simulation should not differ much from the real world if you have the same AoA as it cruises. If you have the right AoA but still the lift is incorrect, then you should check your simulation.
blackmask is offline   Reply With Quote

Old   May 7, 2013, 04:38
Default
  #3
C_K
New Member
 
Myron
Join Date: May 2013
Posts: 4
Rep Power: 4
C_K is on a distinguished road
Quote:
Originally Posted by blackmask View Post
Are you sure that you have the right AoA (angle of attack) ? Lift or cl is much easier to predict so that the result of your simulation should not differ much from the real world if you have the same AoA as it cruises. If you have the right AoA but still the lift is incorrect, then you should check your simulation.
This is at 8 degrees AoA.

The Cl number is correct however the lift force is too low, i am not looking for correct lift force to be honest just the cl and cd.

So Ansys is supposed to give values of lift force of a model close to the real world?

The angle is correct but the mesh because its such as large model has an orthogonal quality of around 0.02. Is that the problem?
C_K is offline   Reply With Quote

Old   May 7, 2013, 10:17
Default
  #4
Senior Member
 
Join Date: Aug 2011
Posts: 315
Rep Power: 12
blackmask will become famous soon enough
How could cl be correct if the lift is too low?
CL = lift/(1/2*rho*U^2*Area)
blackmask is offline   Reply With Quote

Old   May 7, 2013, 11:28
Default
  #5
Far
Super Moderator
 
Far's Avatar
 
Sijal Ahmed Memon (turboenginner@gmail.com)
Join Date: Mar 2009
Location: Islamabad Pakistan
Posts: 3,948
Blog Entries: 6
Rep Power: 39
Far will become famous soon enoughFar will become famous soon enough
Send a message via Skype™ to Far
Quote:
The angle is correct but the mesh because its such as large model has an orthogonal quality of around 0.02. Is that the problem?
minimum allowed quality is 0.01. Would you like to post some pics of mesh?
Far is offline   Reply With Quote

Old   May 7, 2013, 19:26
Default
  #6
C_K
New Member
 
Myron
Join Date: May 2013
Posts: 4
Rep Power: 4
C_K is on a distinguished road
I don't know why the lift force is wrong when the cl is correct.

Cl max for the aircraft at the angle im simulating is 2.1 i got 2.5 which isnt far off.

So is my original question, the lift force should be fairly accurate for the real life model or not? Im new to ansys so please excuse my questions, i though the lift to drag force would just be a component in calculating the cl and cd. Also the cl/cd ratio is good too.

The cl cd values are quite realistic. But not the lift force in newtons.

I dont have the mesh file with me will post it when i do. thanks
C_K is offline   Reply With Quote

Old   May 8, 2013, 11:38
Default
  #7
Senior Member
 
Lefteris
Join Date: Oct 2011
Location: UK
Posts: 192
Rep Power: 5
Aeronautics El. K. is on a distinguished road
Have you analyzed the forces properly? In the monitors panel you have to adjust the direction of the forces.
__________________
Lefteris

Aeronautics El. K. is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[ICEM] Annoying mesh holes on an aircraft Santos-Dumont ANSYS Meshing & Geometry 2 March 2, 2012 09:13
strange node values @ solid/fluid interface - help JB FLUENT 2 November 1, 2008 13:04
node values or cell values? aPpA FLUENT 0 November 10, 2006 09:56
very urgent pleasade:Cl and Cd values for airfoil Liaquat FLUENT 2 April 27, 2006 12:20
Printing Values on a Specific Surface Matthew FLUENT 1 February 8, 2006 09:15


All times are GMT -4. The time now is 17:47.